Fig. 3.

Procedure for preparation of a joint call. Above Spectrogram of an intact natural 3-s-long sequence of calls, produced by a focal silver fox during a human approach test. The sequence contains tonal and noisy calls (labeled with dark bars above the spectrogram), separated with silence spaces (labeled with light bars above the spectrogram). The striped bar labels the superimposed call of a non-focal neighboring fox, produced simultaneously with the call of the focal fox. Below Spectrogram and power spectrum of a part of the future joint call made from the call sequence shown above. Only dark-labeled fragments are reserved, while the light-labeled and strip-labeled are cut off